If you can get double ended, then do it. 250W HQI on real HQI ballasts (m80) with 14K Phoenix bulbs put out as much light as a 20K Radium or 15K Iwasaki for less wattage. 14K Phoenix bulbs last for 2 years. These are best-of-breed type reef lights that you would be very hard pressed to beat. If you keep the top somewhat open with a few small fans, then heat should not be a problem - 3 250W HQI over my 120 doesn't even heat it up 1 degree during the day... and I save about 3KW on running the heaters during that time.